This invention relates generally to fluid control valves provided with positive and negative load compensation.
In more particular aspects this invention relates to pressure compensated direction and flow control valves, the positive and negative load compensators of which are controlled by a single amplifying pilot valve stage.
In still more particular aspects this invention relates to pilot operated pressure compensated controls of direction control valves, used in control of positive and negative load, which permit variation in the level of control differential across metering orifices of the valve spool, while this control differential is automatically maintained constant at each controlled level.
In still more particular aspects this invention relates to pilot operated pressure compensated controls of direction control valves responsive to a manual and an electrical control signal, for control of positive and negative loads, which permit variation in the controlled pressure differential, across metering orifices of the valve spool, in response to an external pulse type control signal.
Closed center fluid control valves, pressure compensated for control of positive and negative loads, are desirable for a number of reasons. They permit load control with reduced power losses and therefore, increased system efficiency. They also permit simultaneous proportional control of multiple positive and negative loads. Such fluid control valves are shown in my U.S. Pat. No. 4,180,098, issued Dec. 5, 1979 and also in my U.S. Pat. No. 4,222,409 issued Sept. 16, 1980. However, the valves of those patents although capable of proportional control of positive and negative loads, use for such control the energy directly transmitted through the load pressure sensing ports, which not only attenuate the control signals, but limit the response of the control. Those valves also automatically maintain a constant pressure differential across metering orifices in control of both positive and negative loads.